Field of the Invention
The present invention relates to wireless communications, and more particularly, to a method and apparatus for controlling uplink transmissions on DRX operation in a wireless communication system.
Discussion of the Related Art
3rd generation partnership project (3GPP) long term evolution (LTE) is an improved version of a universal mobile telecommunication system (UMTS) and a 3GPP release 8. The 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in a downlink, and uses single carrier-frequency division multiple access (SC-FDMA) in an uplink. The 3GPP LTE employs multiple input multiple output (MIMO) having up to four antennas. In recent years, there is an ongoing discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the 3GPP LTE.
Discontinuous reception (DRX) is a method for reducing battery consumption by allowing a user equipment (UE) to discontinuously monitor a downlink channel. When the DRX is configured, the UE discontinuously monitors the downlink channel. Otherwise, the UE continuously monitors the downlink channel.
Recently, many applications require an always-on characteristic. Always-on is a characteristic in which the UE is always connected to a network so as to directly transmit data whenever necessary.
However, since battery consumption is great when the UE continuously maintains the network connection, a proper DRX is configured in a corresponding application to guarantee the always-on characteristic while reducing battery consumption.
Recently, several various applications are running in parallel in one UE, and thus it is not easy to configure one DRX suitable for all of the applications. This is because, even if an optimal DRX is configured for a specific application, it may be a not proper DRX configuration with respect to other applications which are running in parallel.
There is a need for a method for operating the DRX in a more flexible manner and especially, it may be necessary for controlling uplink transmission setup by upper layer on DRX operation.